Changing Shape Color in Visio - shapes

Question

Need some help!
I'm relatively knowledgeable when it comes to macros, VBA, scripts, etc., but Visio coding is an all new monster to me.
In short, I have a warehouse map layout with simple square shapes marking product locations, and I want to color-code the squares based on their Prop._VisDM_F2 data element. My code so far seems to work, but only for the 1st shape in the group of squares, but sometimes the master shape consists of 1 square, sometimes 6, and everything in between.
I've learned that the # in "Shapes(#)" selects which square gets changed, but I want them ALL to change. I've tried to get a count of how many individual shapes are in each master shape to use a variable integer as the #, but it didn't work.
Surely such a simple task can't really this complicated so I'm probably just missing something a step. Any help would be greatly appreciated!
'''
Dim selectObj As Visio.Shape
For Each selectObj In ActiveWindow.Selection
If selectObj.CellExistsU("Prop._VisDM_F2", Visio.VisExistsFlags.visExistsAnywhere) Then
selectObj.Shapes(1).Cells("Fillforegnd").FormulaU = visWhite
End If
Next
End Sub
'''

Answer 1

Shapes can have sub-shapes which are accessed through the Shapes property as per your code (note that most Visio collections are 1 rather than 0 based).
You can address the sub-shapes collection either by index or with a further for each. So given that you may or may not know the depth of your sub-shapes you can recurse through them something like this:
Sub ApplyFillToAll()
Dim shp As Visio.Shape
For Each shp In ActiveWindow.Selection
If shp.CellExistsU("Prop._VisDM_F2", Visio.VisExistsFlags.visExistsAnywhere) Then
SetFill shp, "RGB(255,0,0)"
End If
Next
End Sub
Public Sub SetFill(ByRef shpIn As Visio.Shape, fillFormula As String)
Dim shp As Visio.Shape
For Each shp In shpIn.Shapes
shp.Cells("FillForegnd").FormulaU = fillFormula
SetFill shp, fillFormula
Next
End Sub
Note that the formula that you're setting is a string and so is wrapped in double quotes, and the above will set all of the sub-shapes to red with the SetFill method calling itself to navigate down through the tree.
I'll add a link to a very old post that you might also find useful:
https://visualsignals.typepad.co.uk/vislog/2007/11/looping-through.html